This application claims the priority of Japanese Patent Application No.2000-204309 filed on Jul. 5, 2000, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a continuously variable transmission oil pressure control device and, more particularly, to an oil pressure control device in which the operating characteristic of a valve that is arranged in the continuously variable transmission is improved.
2. Description of the Related Art
Continuously variable transmissions comprising: a drive pulley and a driven pulley freely rotatably journalled within a transmission housing; a belt that transmits rotary force arranged between these pulleys; and an oil pressure actuator used to vary the width of the pulley groove of the drive pulley and driven pulley by moving moveable pulley halves of the drive pulley and driven pulley in the respective pulley axial directions and which is used to change the reduction ratio between the drive pulley side rotary shaft and driven pulley side rotary shaft in continuously variable fashion are employed for example as transmissions for vehicles.
In a continuously variable transmission for a vehicle, a plurality of oil pressure control valves such as a pulley control valve for controlling the groove width of the drive pulley and driven pulley by controlling lateral pressure acting on the moveable pulley half and/or a clutch control valve that effects engagement control of the clutch used in the transmission are employed; these oil pressure control valves are accommodated in the same housing as the continuously variable transmission mechanism comprising the drive pulley and driven pulley, etc., in order to achieve a compact construction of the transmission as a whole. Due to restrictions regarding arrangement space, etc., in some cases the drain ports of such oil pressure control valves are arranged on the line of extension of the circumference of the rotating pulley or the line of extension of the circumference of the rotating belt.
In order to suppress generation of heat resulting from friction between the drive pulley or driven pulley and the belt in the continuously variable transmission mechanism, transmission oil is supplied that lubricates these structural members; this transmission oil used for lubrication/cooling flies off in the circumferential direction of the rotary bodies constituted by the pulleys or the belts and collides with the inside wall of the transmission housing or oil pressure control valves, etc., which are on the line of extension of this circumferential direction. Consequently, if the aperture of the drain port in the oil pressure control valve was in a region on the line of extension of the circumferential direction referred to above, there was the problem that it could easily be affected by splashes of transmission oil flung out from the continuously variable transmission mechanism (the kinetic energy (dynamic pressure) possessed by the splashes acting for example as a back pressure causing fluctuation of the valve).
Construction of an oil pressure control device has been considered in which the valve body in the oil pressure control valve is arranged immersed in transmission oil within an oil pan, the aperture of the drain port in this oil pressure control valve being arranged in an in-oil region. With such a construction, the above problem can be alleviated. However, if the aperture of the drain port was arranged in an in-oil region, when, for example, the ambient temperature was low and the oil viscosity in the oil pan was therefore high, the oil present around the drain port aperture presented resistance to discharge, adversely affecting the response of the oil pressure control valve and leading to problems such as variability of the control characteristic of the controlled member (for example the clutch or drive/driven pulley) with oil temperature, or large moving-off shock when the vehicle moved off. Also, even if the drain port aperture was arranged in an in-oil region, the situation could arise in which the drain port was exposed to splashes by being exposed above the oil surface on shaking of the vehicle, driving while climbing or descending a slope, vehicle acceleration/deceleration, or when the oil surface fell with the viscosity being raised by low oil temperature, etc.
An object of the present invention is to provide a continuously variable transmission oil pressure control device wherein there is no possibility of this being affected by splashes of transmission oil flung out from the continuously variable transmission mechanism, even under such vehicle conditions.
The present invention comprises: a continuously variable transmission comprising: a drive pulley and driven pulley freely rotatably journalled in a housing and respectively having a pair of a fixed pulley half and moveable pulley half, a belt arranged between the drive pulley and driven pulley and that transmits rotational force between the drive pulley and driven pulley; an oil pressure actuator that varies the width of the pulley groove of the drive pulley and the driven pulley by moving the respective moveable pulley halves in the drive pulley and driven pulley in the respective pulley axis directions; wherein, in this continuously variable transmission, there is provided an oil pressure control valve having a drain port that opens in the interior of the housing. In addition, according to the present invention, an oil pressure control device of a continuously variable transmission is constituted wherein the apertures of the drain ports in an oil pressure control valve are arranged outside of the maximum range of movement (for example, belt range) defined by extension in the circumferential direction of the belt of the maximum width, for example the maximum width of the range of movement through which the belt can move in the pulley axis direction, of the range of movement when the pulley groove width of the drive pulley and driven pulley is changed by moving the moveable pulley halves of the drive pulley and driven pulley, and towards the outside of the belt region.
As is well known, the gear-change action in a continuously variable transmission as described above is performed by varying the radius with which the belt is wound on the respective pulleys by changing the width of the pulley grooves (V groove width: separation between the V face of the fixed pulley half and the V face of the movable pulley half of both the drive pulley and driven pulley, which have respectively tapered V-groove faces. The positional relationship of the moveable pulley halves in the drive pulley and driven pulley is usually such that the respective V faces are arranged so as to be opposite on the two pulley shafts which are arranged parallel to each other, so that, when gear-change operation is effected, the belt is moved parallel with the pulley axis direction.
In the above construction according to the present invention, the aperture of the drain port in the oil pressure control valve is arranged outside of the belt region defined by extending the maximum width of the range of movement in which the belt can be moved in the pulley axis direction in the circumferential direction of the belt. The maximum width of the range of movement in which the belt can be moved in the pulley axis direction means the maximum width of the positions which the two ends of the belt can take when a belt having a fixed width in the pulley axis direction is moved in the pulley axis direction by the gear-change operation, and the belt region defined by extending this maximum width in the circumferential direction of the belt means the region in which direct collision with oil splashes flung off by centrifugal force from the rotating belt is possible.
Consequently, with a construction according to the present invention in which the aperture of the drain port in the oil pressure control valve is arranged outside this belt region, an oil pressure control device of a continuously variable transmission can be provided wherein there is no possibility of oil splashes flung off from the rotating belt colliding with the drain port aperture, so there is no possibility of this being subjected to the effect of oil splashes as described above.
According to the present invention, the maximum range of movement defined by extending in the circumferential direction of the drive pulley or driven pulley the range of arrangement of the pulley grooves in which the pulley grooves of the drive pulley or driven pulley can be arranged when the pulley groove width of the drive pulley and driven pulley is varied by moving the moveable pulley halves of the drive pulley and driven pulley, i.e., the groove width region, can be set, the oil pressure control device of the continuously variable transmission being constructed with the aperture of the drain port in the oil pressure control valve being arranged outside of this groove width region.
With the above construction, the aperture of the drain port in the oil pressure control valve is arranged outside the groove width region defined by extending in the circumferential direction of these pulleys the range of arrangement of the pulley groove in which the pulley groove of the drive pulley or driven pulley can be arranged. The range of the arrangement of the pulley groove in which the pulley groove can be arranged means the range in which the pulley groove that is formed by the V face of the fixed pulley half and the V face of the movable pulley half can be arranged; specifically, it means the range defined by the position of the circumferential edge of the V face in the fixed pulley half and the position that can be taken by the circumferential edge of the V face of the movable pulley half when this is moved by a gear-change operation. Specifically, the groove width region defined by extension of the range of arrangement of the pulley grooves in the circumferential direction of the pulleys means the range in which direct collision with oil splashes flung out from the circumferential edges of the V faces after traveling over the V faces of the rotating pulleys is possible.
Consequently, with a construction according to the present invention in which the aperture of the drain port in the oil pressure control valve is arranged outside the groove width region, a continuously variable transmission oil pressure control device can be provided in which there is no possibility of collision of oil splashes flung out from the rotating drive pulley or driven pulley with the drain port aperture, and which is, therefore, not subject to the effects of oil splashes as described above. If the groove width regions are different as between the drive pulley and driven pulley, depending on the positional relationship with the aperture of the drain port, etc., outside of either one of the groove width regions may be designated or outside of both of the groove width regions may be designated.
In the above construction, preferably the continuously variable transmission oil pressure control device is constructed such that the valve body of the oil pressure control valve is immersed in the oil constituting the fluid that is the subject of control in the bottom part of the interior of the housing (for example in this embodiment, the transmission oil), and the aperture of the drain port opens above the oil surface. With this construction, because the valve body of the oil pressure control valve is immersed in the oil, there is no possibility of air being sucked into the valve, yet, since the aperture of the drain port is formed above the oil surface, even if the oil viscosity is high due to low oil temperature, there is no possibility of the response of the oil pressure control valve being adversely affected by resistance to discharge by surrounding oil. Consequently, a continuously variable transmission oil pressure control device can be provided that cannot be affected by splashes of transmission oil flung out from the transmission mechanism and wherein the control characteristic of the items of equipment to be controlled is little changed by the temperature of the transmission oil.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.